Field emission displays are well known in the art. A field emission display includes an anode plate and a cathode plate that define a thin envelope. The anode plate and cathode plate can be separated by dielectric spacer structures. The cathode plate includes column electrodes and gate extraction electrodes, which are used to cause selective electron emission from electron emitters, such as Spindt tips or emissive surfaces.
The separation distance between the anode plate and the cathode plate has a lower limit. The minimum distance is determined by the break down voltage of the dielectric spacer structures and by the need to avoid arcing between the anode plate and the cathode plate. Especially at high anode voltages, the minimum separation distance can result in electron beams that have unacceptably large cross-sections at the anode plate. It is known in the art to use additional electrically conductive layers or electrically resistive layers for the purpose of focusing the electron beams to achieve a desired cross-section at the anode plate. Benefits, such as improved resolution of a display image, can be realized by the focusing.
It is also known in the art to use an electrically conductive or electrically resistive layer, which circumscribes an emissive surface, for reducing leakage currents at the gate extraction electrode.
However, the use of these additional layers can result in problems, such as suppression of the electric field at the electron emitter as well as unacceptable, spurious electron emission from the additional material.
Accordingly, there exists a need for a field emission display having an improved focusing structure, which overcomes at least some of these shortcomings.